Plasma enhanced chemical vapor deposition (PECVD) is a low pressure materials deposition technique in which thin films with highly tailored properties and functionality can be deposited onto a substrate. PECVD is most widely used in the semiconductor industry for the deposition of silicon dioxide onto wafers containing metal layers and other temperature sensitive structures. Typically PECVD reactors operate at very low pressures (e.g., a fraction of a Torr). The plasma is necessarily non-equilibrium and non-thermal, with high energy electrons and neutral atoms at near ambient temperature. Through collisions, the high electron energy allows for the creation of the chemically reactive species which form the deposited film. The low neutral temperature prevents thermal damage of the substrate.
Over the past decade, advances in the understanding of non-equilibrium, ‘cold’, atmospheric pressure plasmas have led researchers to investigate the possibilities of atmospheric pressure PECVD. The main reasons for pursuing research in AP-PECVD were: 1) lower operating cost, due to the lack of expensive vacuum processing equipment; 2) higher deposition rates, due to the higher densities of operation; and 3) continuous processing, due to the relaxation of the requirement to process substrates in batch mode.
While most research in the area of AP-PECVD has focused on alternative methods to current low pressure processing techniques, such as SiO2 film deposition, the use of non-thermal plasmas for the treatment of living organisms is a recent and exciting field. Significant findings have been made in the sterilization of surfaces from bacteria based on exposure to plasma. More recently, plasma sterilization has been shown in animal and human studies. Non-thermal plasma has also been shown to enable tissue bonding through thermal coagulative bonding, chemical denaturing bonding, and blood coagulation bonding. Most of these applications of plasma to biological substrates have used gases consisting of mixtures of air with noble gases.
While several beneficial effects from the exposure of biological materials to non-thermal plasma have been noted, the interaction of reacting chemistries (beyond those of air's constituents) with biological surfaces and deposition onto living substrates has not yet been investigated. There is therefore a need in the art to develop a mechanism by which living substrates may be exposed to non-thermal plasma containing different chemical constituents and by which plasma-generated films may be deposited on these surfaces.